Slide rule



Nov. 22, 1966 Y L. A. WARNER SLIDE RULE Filed July 15, 1965 INVENTOR.

Y Louis .4. Warner B I A TTORNE YS United States Patent 3,286,920 SLIDE RULE Louis A. Warner, 5223 N. Natoma, Chicago, Ill. Filed July 15, 1965, Ser. No. 472,092 4 Claims. (Cl. 235-70) This invention relates, in general, to slide rules and more particularly to collapsible slide rules which may be rolled up for storage or for conveniently transporting them.

It is generally well known with slide rules, that the longer the length of the slide rule, or the greater the diameter in the case of a circular slide rule, the greater will be the ability to interpolate to determine additional significant figures. Accordingly, by the same token, the accuracy of the slide rule is increased, depending, of course, on the ability of the user.

The most popular slide rule, in all probability, is the -inch slide rule since it is a convenient size to carry and store in a desk drawer, and the scales which can be provided on it are of suflicient size to assure reasonable accuracy. Many longer in length, for example, 36- inch, slide rules are available and are used when greater accuracy is required, but their use is generally confined to laboratories and the like because of their size.

The longer slide rules are also preferred by users whose eyesight is not as good as it should be, since the scales are expanded to a greater degree and are therefore easier to read.

Anyone who uses a large slide rule is generally inconvenienced by having to cope with how to store them when not in use, or how to carry them when travelling. It would therefore be particularly advantageous in the above cases to have a slide rule which is long in length, but which can be easily carried and stored.

Accordingly, it is an object of the present invention to provide a slide rule which may be of any length, but which is collapsible in that it can be rolled up, so that it can be easily and conveniently carried and stored.

It is another object of the present invention to provide a slide rule of the above type which is collapsible by rolling it up, into a compact unit.

It is still another object of the present invention to provide a collapsible slide rule which can be rolled up and which has a cursor slider which is adapted to function as a storage and carrying case for the slide rule.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combination of elements, and arrangements of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

The above objectives are accomplished with a slide rule which according to the present invention comprises a main body portion and a slider portion, each of which is fabricated in the form of a spring constructed of a flat band of a ribbon formed into a spiral coil. The spring is characterized as a coil composed of a flat ribbon stressed to assume a plurality of tightly wound convolutions when the coil is in its reposed condition. Also, the spring is formed with a cross curvature such that it may be unwound and will remain in a balanced extending configuration and will automatically rewind into its convoluted condition when the spring is flexed in opposition to its natural cross curvature when unwound or extended. In this respect, the spring comprising the body portion and the sliding portion of the present invention is preferably of the type disclosed in US. Patent 2,956,795 issued October 18, 1960, to Edwin E. Foster. A cursor slider is provided which is adapted to fixedly retain the body portion and the slider portion in working relationship with one another and, in accordance with one embodiment of the invention the cursor slider is constructed in a fashion such as to providea carrying case for the slide rule when the latter is collapsed by rolling it up.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a top plan view of a slide rule exemplary of the present invention, the slide rule being broken away to illustrate its opposite extreme ends;

FIGURE 2 is an end view of the slide rule of FIG. 1;

FIGURE 3 is a perspective View of the cursor slider of the slide rule of FIG. 1;

FIGURE 4 is a view illustrating a cursor slider constructed in accordance with a second embodiment of the invention, to provide a self-storing carrying case for the slide rule when the latter is collapsed by rolling it up;

FIGURE 5 is an end view of the cursor slider of FIG. 4;

FIGURE 6 is a view illustrating the configuration of one of the two portions of the slide rule of FIG. 1, partially collapsed and rolled up; and

FIGURE 7 is a sectional view of the collapsed and rolled up portion of the slide rule illustrated in FIG. 6.

Similar reference characters refer to similar parts throughout the several views of the drawing.

Referring now to the drawings, in FIG. 1 there is shown a slide rule 10 exemplary of the present invention having a body portion 12, a smaller in width slider portion 14 and a cursor slider 16. In general, the body portion 12 and the slide portion 14 of the slide rule 10 each have one or more scales provided thereon for solving mathematical problems, in the well known manner.

The body ortion 12 and the slide portion 14 of the slide rule 10 are formed of springs of the type disclosed in the above mentioned US. Patent 2,956,795 and, in particular, the spring shown in FIGS. 7 and 8. In FIG. 6 the spring forming the body portion 12, or the slide portion 14, is shown and generally denoted by the numeral 18. The spring 18 is constructed from a ribbon 20 stressed for a substantial portion of its length to form a plurality of tightly wound convolutions when in its reposed condition. A cross section 22 taken from an unstressed portion 24 shows that the ribbon prior to stressing had a cross-sectional curvature in which the concave side was away from the center of the coil 26.

A cross section 28 taken from an extended portion 30 of the stressed ribbon shows a resultant cross-sectional curvature in which the concave side is away from the center of the coil. It will be noticed that the cross curvature shown in cross-section 28 is somewhat less than that shown in cross-section 22. As explained in the above identified patent, this appears to be the result of the opposing nature of the formed cross-section and the natural cross-section so that there is a subtractive relationship. As can be best seen in FIG. 7, the ribbon 20 when in the coiled condition has a substantially flat cross-section. In other words, the cross-sectional curvature shown in the cross-section 28 must be flattened out as the ribbon is allowed to re-wind from the extended condition to the coiled condition.

Also, as explained in the above identified patent, the strength of the spring 30 depends upon the relationship of the cross component to the longitudinal component. The stresses which tend to cause the ribbon to assume a tightly Wound configuration is referred to as the longitudinal component and the force required to flatten the cross curvature is referred to as the cross component. If the amount of resultant cross curvature is less than the natural cross curvature, that is, the concave-convex crosssection that occurs notwithstanding the fact that the coil spring is constructed from a ribbon having a substantially flat cross-section, then the spring 30 will be somewhat stronger than the strength of a spring having a natural cross curvature. If the cross curvature of the spring 18 15 of such an amount that it is substantially equal to the longitudinal component of the spring, it would take a force of zero magnitude to maintain the spring in its extended condition. The stressed ribbon in this type of spring may be readily removed from the coil whereupon it will form the cross-sectional curvature. If it should be desired to rewind the stress ribbon onto the coil, it is merely necessary to hold a coil portion and apply a slight force toward the coil at the other end. If the coil is allowed to rotate, then the unwound stressed ribbon will readily wind onto the coil. For the purposes of the present invention, the cross curvature is preferably of such an amount that it is substantially equal to the longitudinal component of the spring so that a force of zero magnitude is required to maintain the spring in its extended condition. The preceding is a general description of the spring forming the body portion 12 and the slide portion 14 of the slide rule 10 and reference may be had to the above identified patent for a more detailed and specific explanation of the construction of the spring 18.

As further explained in the above identified patent, the spring 18 when fully extended will tend to remain in its extended condition even if unrestrained. This tendency to remain in the extended condition is at least partially dependent upon the magnitude of the resultant cross curvature. If the resultant cross curvature is relatively large, the stability of the spring when in the extended condition will be greater than if it is relatively small for any given longitudinal component. When such a spring is in the extended condition, it may be recoiled by bending the ribbon in the direction of the coil so as to partially form a first convolution. If the spring is of the selfwinding type, then it will continue Winding until all of the stressed ribbon has been wound into the coiled condition.

The springs forming the body portion 12 and the slide portion 14 are both formed with the same cross curvature so that the curvature of the slide portion 14 corresponds to that of the body portion 12 and the slide portion 14 will rest atop the body portion 12, in the manner illustrated in FIG. 2. The cursor slider 16 is preferably rectangular in shape and is molded as an integral unit, of transparent plastic or the like. A hair-line 40 is provided on the top surface of the cursor slider 16. As can be best seen in FIG. 2, the cursor slider 16 has two slots 41 and 42 formed therein which extend through it transversely to the hair-line 40. The slot 42 has a height and a width which corresponds to the configuration of the stressed spring forming the slider portion 14 and is centrally positioned with respect to the slot 41 so that the slide portion 14 is centrally positioned with respect to the body portion 12. The slots 41 and 42 preferably are formed so that the top edge of the slot 42 bears somewhat against the upper surface of the slide portion 14 so that it is urged against the body portion 12 and its edges are firmly engaged with the side edges of the slot 42. The body portion 12 is also preferably urged into the lower corners of the slot 41. When constructed in the above described manner, the cursor slider 16 securely retains the slider portion 14 and the body portion 12 in working relationship with one another.

In some applications, particularly when the slide rule 10 is extremely long in length, it may be desirable to additionally provide a slider having a configuration conforming to that of the cursor slider 16 at one or both ends of the slide rule 10, to retain the body portion 12 and slider portion 14 in working relationship.

In FIGS. 4 and there is illustrated a combination cursor slider and storage case 50 having a circular side wall 51 and a bottom wall 52 forming a closable circular storage area 53, A correspondingly shaped cover 54 is pivotally secured by means of a pivot pin 55 to the edge of the side wall 51 for completely enclosing the storage area 53. A lock tab 56 may be formed at a point on the periphery of the cover 54 and a correspondingly shaped recess 58 positioned so as to lock the cover 54 in a closed position. The cursor slider 16 is integrally formed with the side wall 51, at a point about the exterior periphery of the side wall. The slide rule 10 may be collapsed by rolling it up into a coil, such as the coil 26, and stored within the combination cursor slider and carrying case 59.

From the above description it is apparent that a slide rule of any length, for example 36 inches, can be provided so that all of the advantages derived from the longer length are available to a user. The slide rule is operated, as any slide rule, by sliding the slide portion 14 transversely along the length of the body portion 12 to align the indicia of one scale with that of another scale and by positioning the cursor slider 16, as required to solve the mathematical computation. To store the slide rule 10, in the case of the slide rule shown in FIG. 1, the ends of the slide portion 14 are aligned with the ends of the body portion 12, the cursor slider 16 slid to one extreme end and both springs simultaneously recoiled by bending the ribbons in the direction of the coil so as to partially form a first convolution. The springs will continue winding until all of the stressed ribbons have been wound into the coiled condition. In the case of the combination cursor slider and carrying case 50, the springs constituting the body portion 12 and the slide portion 14 are removed from the slots 41 and 42 of the cursor slider 16 wound into a coil such as the coil 26 and placed within the storage area 53 of carrying case cursor. A slide rule constructed in the manner described above, regardless of its length, can therefore be easily stored within a desk drawer or the like and easily carried with an individual.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.

Now that the invention has been described, what is claimed as new and desired to be secured by Letters Pat ent is:

1. A slide rule comprising a body portion, a narrower in width slider portion adapted to slidably fit atop said body portion and a cursor slider, said body portion and said slider portion each having at least one scale thereon for solving mathematical computations and formed of a coiled spring comprising a ribbon having a formed concave-convex cross-section, permanently stressed into a plurality of tightly wound convolutions when said stressed ribbon is in repose, each of said convolutions engaging the preceding convolution when said stressed ribbon is in repose, the convex side of said concave-convex cross-section facing towards the center of the coiled spring, said cursor slider having a pair of slots extending therethrough for receiving and retaining said slider portion in working relationship atop said body portion, whereby mathematical computations can be made by manipulating them and said body portion and said slider portion collapsed by rolling them up.

2. A slide rule comprising a body portion, a narrower in width slider portion adapted to slidably fit atop said body portion and a cursor slider, said body portion and said slider portion each having at least one scale thereon for solving mathematical computations and formed of a coiled spring comprising a ribbon permanently longitudinally stressed into a plurality of contiguous convolutions when in repose, said stressed ribbon having a longitudinal stress component when extended from its convoluted condition, said longitudinal stress component tending to cause a natural concave-convex cross-section in said stressed ribbon and further tending to cause said stressed ribbon to return to its convoluted condition, said stressed ribbon also formed to have a tendency when extended to assume a concave-convex cross-section in which the convex side is toward the center of the coil, said ribbon being forced to assume a substantially flat cross-section when said extended portion is wound into its coiled condition, the flattening of said concave-convex cross-section forming a cross stress component in opposition to said tendency to return to said convoluted condition resulting from the longitudinal stress component, said cross stress component being dependent upon the magnitude of cross-sectional curvature when said stressed ribbon is in the extended condition, said cross stress component being substantially equal to said longitudinal stress component whereby said stressed ribbon when unrestrained will remain in the extended position or the convoluted condition, said cursor slider having a pair of slots extending therethrough for receiving and retaining said slider portion in working relationship atop said body portion, whereby mathematical computations can be made by manipulating them and said body portion and said slider portion collapsed by rolling them up.

3. The slide rule of claim 2 wherein said pair of slots are centrally disposed one atop the other, whereby said slider portion is retained centrally disposed atop said body portion *4. The slide rule of claim 2 wherein said cursor slider is formed as an integral part of a storage case having a closable storage portion in which said slide rule can be stored when collapsed.

References Cited by the Examiner UNITED STATES PATENTS 937,863 10/1909 Roberts. 2,091,661 8/1937 Von Forster et a1. 2,615,630 10/1952 Eckel. 20 2,956,795 10/1960 Foster 33--138 X RICHARD B. WILKINSON, Primary Examiner.

LEO SMILOW, Examiner.

25 J. G. MURRAY, Assistant Examiner. 

1. A SLIDE RULE COMPRISING A BODY PORTION, A NARROWER IN WIDTH SLIDER PORTION ADAPTED TO SLIDABLY FIT ATOP SAID BODY PORTION AND A CURSOR SLIDER, SAID BODY PORTION AND SAID SLIDER PORTION EACH HAVING AT LEAST ONE SCALE THEREON FOR SOLVING MATHEMATICAL COMPUTATIONS AND FORMED OF A COILED SPRING COMPRISING A RIBBON HAVING A FORMED CONCAVE-CONVEX CROSS-SECTION, PERMANENTLY STRESSED INTO A PLURALITY OF TIGHTLY WOUND CONVOLUTIONS WHEN SAID STRESSED RIBBON IS IN REPOSE, EACH OF SAID CONVOLUTIONS ENGAGING THE PRECEDING CONVOLUTION WHEN SAID STRESSED RIBBON IS IN REPONSE, THE CONVEX SIDE OF SAID CONCAVE-CONVEX CROSS-SECTION FACING TOWARDS THE CENTER OF THE COILED SPRING, SAID CURSOR SLIDER HAVING A PAIR OF SLOTS EXTENDING THERETHROUGH FOR RECEIVING AND RETAINING SAID SLIDER PORTION IN WORKING RELATIONSHIP ATOP SAID BODY PORTION, WHEREBY MATHEMATICAL COMPUTATIONS CAN BE MADE BY MANIPULATING THEM AND SAID BODY PORTION AND SAID SLIDER PORTION COLLAPSED BY ROLLING THEM UP. 